other than the fact that i find this control scheme in isometrics awkward, this was more or less perfect.
i sure would have liked an overworld/hub type deal though.
if you wanted to expand on this i'd make an overworld with portals to worlds each with some amount of levels, each world with its own theme, which could be as simple as a defining mechanic, a color scheme, and a unique ambient noise or track.
would be cool but obviously well beyond the scope of what's been done here so it's a lot to ask/suggest. either way great job.